1. Field of the Invention
The present invention relates to a wipe sampling assembly used for an ion mobility spectrometer to collect particulate samples on the surface of an article.
2. Description of the Related Art
Ion mobility spectrometry is a rapid, sensitive and portable technique for field detection. The technique has been widely applied by military and security inspection agencies to detect toxic chemical agents, explosives, illicit drugs etc.
When an ion mobility spectrometer is used to detect contraband materials, a particulate sampling method is most usually employed. A swab is swiped over the surface of an article to collect any particles of explosives or drugs and the swab inserted into the inlet port of the spectrometer. The analyte is then thermally desorbed from the swipe, enter the ionization chamber and pass along the drift tube where they are detected and identified.
At present, there are mainly two types of particulate sampling modes adopted by the ion mobility spectrometer:
1. A Wipe Sampling Mode in which the Swab is Held with a Hand During Wiping and Sampling
The above wipe sampling mode is performed by using a hand to hold the swab directly and swipe over a surface for sample collection. In order to prevent the hand from contacting the surface (since the contaminated hand may interfere with sample collection and detection), the swab and the corresponding inlet port has to be made large. It will not only cause a waste of swabs, but more importantly, heat can not be concentrated so that heating efficiency will be greatly reduced due to the large-sized inlet, which may adversely affect the detection sensitivity of the spectrometer. Moreover, more electrical energy is needed. Accordingly, the operating time of a battery will be shortened, thereby leading to the performance degradation of the instrument. In addition, since the swab contacts directly with the hand, dust-free gloves must be worn and frequently replaced to prevent a cross contamination between the hand and the swab so that the sampling operation is very inconvenient.
2. A Wipe Sampling Mode in which a Sampling Strip is Gripped by a Wiping Device During Wiping and Sampling
The above wipe sampling mode uses smaller sampling swabs which are suitable to an ion mobility spectrometer with a small inlet port. However, since a dedicated wiping device is used, the sampling operation is still inconvenient.